A Mechanistic-Based and Non-invasive Approach to Quantify the Capability of Kidney to Detoxify Cysteine-Disulfides.

Our general goal was to non-invasively evaluate kidney tubular dysfunction. We developed a strategy based on cysteine (Cys) disulfide stress mechanism that underlies kidney dysfunction. There is scarce information regarding the fate of Cys-disulfides (CysSSX), but evidence shows they might be detoxified in proximal tubular cells by the action of N-acetyltransferase 8 (NAT8). This enzyme promotes the addition of an N-acetyl moiety to cysteine-S-conjugates, forming mercapturates that are eliminated in urine. Therefore, we developed a strategy to quantify mercapturates of CysSSX in urine as surrogate of disulfide stress and NAT8 activity in kidney tubular cells. We use a reduction agent for the selective reduction of disulfide bonds. The obtained N-acetylcysteine moiety of the mercapturates from cysteine disulfides was monitored by fluorescence detection. The method was applied to urine from mice and rat as well as individuals with healthy kidney and kidney disease.

AHR canonical pathway: in vivo findings to support novel antihypertensive strategies.

Essential hypertension (HTN) is a disease where genetic and environmental factors interact to produce a high prevalent set of almost indistinguishable phenotypes. The weak definition of what is under the umbrella of HTN is a consequence of the lack of knowledge on the players involved in environment-gene interaction and their impact on blood pressure (BP) and mechanisms. The disclosure of these mechanisms that sense and (mal)adapt to toxic-environmental stimuli might at least determine some phenotypes of essential HTN and will have important therapeutic implications. In the present manuscript, we looked closer to the environmental sensor aryl hydrocarbon receptor (AHR), a ligand-activated transcription factor involved in cardiovascular physiology, but better known by its involvement in biotransformation of xenobiotics through its canonical pathway. This review aims to disclose the contribution of the AHR-canonical pathway to HTN. For better mirror the complexity of the mechanisms involved in BP regulation, we privileged evidence from in vivo studies. Here we ascertained the level of available evidence and a comprehensive characterization of the AHR-related phenotype of HTN. We reviewed clinical and rodent studies on AHR-HTN genetic association and on AHR ligands and their impact on BP. We concluded that AHR is a druggable mechanistic linker of environmental exposure to HTN. We conclude that is worth to investigate the canonical pathway of AHR and the expression/polymorphisms of its related genes and/or other biomarkers (e.g. tryptophan-related ligands), in order to identify patients that may benefit from an AHR-centered antihypertensive treatment.

First evidence of aryl hydrocarbon receptor as a druggable target in hypertension induced by chronic intermittent hypoxia.

BACKGROUND AND PURPOSE: Obstructive sleep apnea (OSA) is associated to a high prevalence of resistant arterial hypertension (HTN) justifying the research on novel targets. Chronic intermittent hypoxia (CIH) is a key feature in the development of OSA comorbidities, including HTN. EXPERIMENTAL APPROACH: We used a rat model of CIH-induced HTN to disclose the hypothesis that the aryl hydrocarbon receptor (AHR) is activated by CIH once it shares the same binding partner of HIF-1α and promotes pro-oxidant, pro-inflammatory (NF-kB) and pro-fibrotic events in common with CIH. KEY RESULTS: Upon established hypertension (21 days exposure to CIH), we observed an increase in Cyp1a1 mRNA in kidney cortex (6-fold), kidney medulla (3-fold) and liver (3-fold), but not in other tissues. Increased renal expression of Ahr and markers of inflammation (Rela), epithelial to mesenchymal transition markers, the rate-controlling step of gluconeogenesis, Pepck1, and members of HIF-pathway, namely, Hif3a were also observed. Daily administration (14 days) of AHR antagonist, CH-223191 (5 mg.kg-1.day-1, gavage), simultaneously to CIH prevented the increase in systolic blood pressure (SBP) by 53 ± 12% and in diastolic blood pressure (DBP) by 44 ± 16%. Moreover, its administration (14 days) upon already established HTN reversed the increase in SBP by 52 ± 12%. CONCLUSION AND IMPLICATIONS: CIH caused an activation of AHR signaling particularly in the kidney and its pharmacological blockade had a significant impact reverting already established HTN. This first evidence inspires innovative research opportunities for the understanding and treatment of this particular type of HTN.

The mercapturomic profile of health and non-communicable diseases.

The mercapturate pathway is a unique metabolic circuitry that detoxifies electrophiles upon adducts formation with glutathione. Since its discovery over a century ago, most of the knowledge on the mercapturate pathway has been provided from biomonitoring studies on environmental exposure to toxicants. However, the mercapturate pathway-related metabolites that is formed in humans-the mercapturomic profile-in health and disease is yet to be established. In this paper, we put forward the hypothesis that these metabolites are key pathophysiologic factors behind the onset and development of non-communicable chronic inflammatory diseases. This review goes from the evidence in the formation of endogenous metabolites undergoing the mercapturate pathway to the methodologies for their assessment and their association with cancer and respiratory, neurologic and cardiometabolic diseases.

Mercapturate Pathway in the Tubulocentric Perspective of Diabetic Kidney Disease.

BACKGROUND: The recent growing evidence that the proximal tubule underlies the early pathogenesis of diabetic kidney disease (DKD) is unveiling novel and promising perspectives. This pathophysiological concept links tubulointerstitial oxidative stress, inflammation, hypoxia, and fibrosis with the progression of DKD. In this new angle for DKD, the prevailing molecular mechanisms on proximal tubular cells emerge as an innovative opportunity for prevention and management of DKD as well as to improve diabetic dysmetabolism. SUMMARY: The mercapturate pathway (MAP) is a classical metabolic detoxification route for xenobiotics that is emerging as an integrative circuitry detrimental to resolve tubular inflammation caused by endogenous electrophilic species. Herein we review why and how it might underlie DKD. Key Messages: MAP is a hallmark of proximal tubular cell function, and cysteine-S-conjugates might represent targets for early intervention in DKD. Moreover, the biomonitoring of urinary mercapturates from metabolic inflammation products might be relevant for the implementation of preventive/management strategies in DKD.

Efavirenz biotransformation as an up-stream event of mood changes in HIV-infected patients.

Efavirenz is a drug of choice for adults and children infected with the human immunodeficiency virus. Notably, up to 35% of patients on efavirenz suffer from mood changes. This work aimed to investigate efavirenz biotransformation into 8-hydroxy-efavirenz as an up-stream event of mood changes and to evaluate the suitability of 8-hydroxy-efavirenz biomonitoring for the minimization of these manifestations. A case-control study with two age-matched groups of HIV-infected male patients was performed in a group without adverse central nervous system complaints (28 patients) and a group presenting mood changes (14 patients). The plasma concentration of non-conjugated 8-hydroxy-efavirenz was higher in patients with mood changes (p=0.020). An association between efavirenz and 8-hydroxy-efavirenz-glucuronide was found (Spearman r=0.414, p<0.010), only within therapeutic efavirenz concentrations. This correlation was not observed in patients with toxic (>4mg/L) plasma concentrations of the parent drug. We conclude that metabolism to 8-hydroxy-efavirenz is associated with efavirenz-related mood changes, which suggests that the concentration of this metabolite is a suitable parameter for therapeutic drug monitoring aimed at controlling these manifestations. Moreover, our data suggest that 8-hydroxy-efavirenz is able to cross the blood-brain barrier and that the peripheral detoxification of 8-hydroxy-efavirenz by glucuronidation may be inhibited by toxic efavirenz concentrations.